Generics in transplantation medicine: Randomized comparison of innovator and substitution products containing mycophenolate mofetil

Generic Medicinal Products in Immunosuppressive Therapy-Should It be a Challenge for Therapeutic Drug Monitoring?

ABSTRACT

Immunosuppressants have a narrow therapeutic index (NTIDs). Indisputably cyclosporine, tacrolimus, everolimus, and sirolimus have NTIDs, and only in the case of mycophenolic acid, a scientific discussion has not been yet concluded. Their specificities highlight the implications for generics introduced into the drug market, more precisely, with bioequivalence testing. In the European Union, the European Medicines Agency (EMA) released the "Guideline on the Investigation of Bioequivalence." The bioequivalence (BE) of the generic (tested, T) versus original (reference, R) product should be confirmed by obtaining a 90% confidence interval (CI) for the T:R ratio of each of the 2 decisive pharmacokinetic parameters, namely, the area under the curve (AUC) between 90.00% and 111.11%. A similar approach (90.00%-112.00%) for AUC was adopted by the Canadian Agency for Drugs and Technologies in Health (CADTH) for NTIDs; however, the US Food and Drug Administration is still based on classic acceptance criteria: 90% CI between 80.00% and 125.00% but with special requirements of BE testing. A discussion about long-expected global consensus was performed in this study based on the literature concerning BE testing in the case of NTIDs. The narrow acceptance criteria reduce the potential mean difference in bioavailability between generic and original products by a few percent. To identify this problem, special attention has been paid to switching drugs (generic-generic, original-generic) and therapeutic drug monitoring after conversion (TDM). There is no global consensus on the acceptance criteria for the BE of generic drugs; therefore, consensus and harmonization are strictly necessary. This study presents a review of the generic drug market and its classification by manufacturers, drug agencies, and dates of marketing authorization. Guidelines for TDM optimization (during switching/conversion) have been proposed. Physicians and clinical pharmacists should pay special attention to switching immunosuppressive drugs between original versus generic formulations, and generic versus generic formulations. Patients and their families should be educated on the risks associated with uncontrolled conversion.

Mycophenolate mofetil versus azathioprine in kidney transplant recipients on steroid-free, low-dose cyclosporine immunosuppression (ATHENA): A pragmatic randomized trial

BACKGROUND

We compared protection of mycophenolate mofetil (MMF) and azathioprine (AZA) against acute cellular rejection (ACR) and chronic allograft nephropathy (CAN) in kidney transplant recipients on steroid-free, low-dose cyclosporine (CsA) microemulsion maintenance immunosuppression.

METHODS AND FINDINGS

ATHENA, a pragmatic, prospective, multicenter trial conducted by 6 Italian transplant centers, compared the outcomes of 233 consenting recipients of a first deceased donor kidney transplant induced with low-dose thymoglobulin and basiliximab and randomized to MMF (750 mg twice/day, n = 119) or AZA (75 to 125 mg/day, n = 114) added-on maintenance low-dose CsA microemulsion and 1-week steroid. In patients without acute clinical or subclinical rejections, CsA dose was progressively halved. Primary endpoint was biopsy-proven CAN. Analysis was by intention to treat. Participants were included between June 2007 and July 2012 and followed up to August 2016. Between-group donor and recipient characteristics, donor/recipient mismatches, and follow-up CsA blood levels were similar. During a median (interquartile range (IQR)) follow-up of 47.7 (44.2 to 48.9) months, 29 of 87 biopsied patients on MMF (33.3%) versus 31 of 88 on AZA (35.2%) developed CAN (hazard ratio (HR) [95% confidence interval (CI)]: 1.147 (0.691 to 1.904, p = 0.595). Twenty and 21 patients on MMF versus 34 and 14 on AZA had clinical [HR (95% CI): 0.58 (0.34 to 1.02); p = 0.057) or biopsy-proven subclinical [HR (95% CI): 1.49 (0.76 to 2.92); p = 0.249] ACR, respectively. Combined events [HR (95% CI): 0.85 (0.56 to 1.29); p = 0.438], patient and graft survival, delayed graft function (DGF), 3-year glomerular filtration rate (GFR) [53.8 (40.6;65.7) versus 49.8 (36.8;62.5) mL/min/1.73 m2, p = 0.50], and adverse events (AEs) were not significantly different between groups. Chronicity scores other than CAN predict long-term graft outcome. Study limitations include small sample size and unblinded design.

CONCLUSIONS

In this study, we found that in deceased donor kidney transplant recipients on low-dose CsA and no steroids, MMF had no significant benefits over AZA. This finding suggests that AZA, due to its lower costs, could safely replace MMF in combination with minimized immunosuppression.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00494741; EUDRACT 2006-005604-14.

Personalized Therapy for Mycophenolate: Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

ABSTRACT

When mycophenolic acid (MPA) was originally marketed for immunosuppressive therapy, fixed doses were recommended by the manufacturer. Awareness of the potential for a more personalized dosing has led to development of methods to estimate MPA area under the curve based on the measurement of drug concentrations in only a few samples. This approach is feasible in the clinical routine and has proven successful in terms of correlation with outcome. However, the search for superior correlates has continued, and numerous studies in search of biomarkers that could better predict the perfect dosage for the individual patient have been published. As it was considered timely for an updated and comprehensive presentation of consensus on the status for personalized treatment with MPA, this report was prepared following an initiative from members of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT). Topics included are the criteria for analytics, methods to estimate exposure including pharmacometrics, the potential influence of pharmacogenetics, development of biomarkers, and the practical aspects of implementation of target concentration intervention. For selected topics with sufficient evidence, such as the application of limited sampling strategies for MPA area under the curve, graded recommendations on target ranges are presented. To provide a comprehensive review, this report also includes updates on the status of potential biomarkers including those which may be promising but with a low level of evidence. In view of the fact that there are very few new immunosuppressive drugs under development for the transplant field, it is likely that MPA will continue to be prescribed on a large scale in the upcoming years. Discontinuation of therapy due to adverse effects is relatively common, increasing the risk for late rejections, which may contribute to graft loss. Therefore, the continued search for innovative methods to better personalize MPA dosage is warranted.

Important considerations for drugs, nutritional, and herbal supplements in pediatric solid organ transplant recipients

Pediatric transplant recipients are on multiple prescription and non-prescription drugs. Many patients also use dietary, nutritional, and herbal supplements. This manuscript researched formulations of immunosuppressive drugs currently available and presents information on generic immunosuppressive drugs, commonly used non-prescription medications, dietary supplements, and herbal supplements. Immunosuppressive drugs are available in various formulations. Not all formulations are interchangeable. A number of FDA-approved generic formulations are available commercially in the United States. Generally generic formulations produce similar blood concentration vs time profiles compared to brand name products in adults and are considered to be bioequivalent. NSAID should be avoided in transplant patients due to potential drug interactions and increased risk associated with NSAID use; and appropriate doses of acetaminophen should be used for treatment of pain. Over-the-counter medications, such as guaifenesin and dextromethorphan, antihistamine medications, including diphenhydramine, loratadine, cetirizine, and fexofenadine, can be safely used in pediatric solid organ transplant population. Many safe and effective over-the-counter options exist for stool softening and as laxative. Diarrhea can lead to an increase in calcineurin inhibitor levels. Food can alter the absorption of immunosuppressive drugs. Several herbal products can alter immune status of the patients or alter the blood concentration of immunosuppressive drugs or may produce renal or hepatic toxicities and should be avoided in pediatric transplant recipients. It is important to educate pediatric transplant recipients and their families about not only immunosuppressive drug therapy but also about non-prescription drugs, dietary, and herbal supplement use.

Investigating a Modified Apparatus to Discriminate the Dissolution Capacity In Vitro and Establish an IVIVC of Mycophenolate Mofetil Tablets in the Fed State

In this study, a modified dissolution apparatus was developed by equipping a USP apparatus Ⅰ with an open-loop system to discriminate the dissolution capacity in vitro and establish an in vitro and in vivo correlation (IVIVC) for mycophenolate mofetil (MMF) tablets. MMF had strong pH-dependent solubility that could influence the dissolution rate in vivo after the meal. Dissolution tests involving reference (Cellcept®) and test formulations (F1 and F2) were conducted using pH 4.5 acetate buffer to simulate gastric fluids in the fed state. The dissolution profiles of the reference and test formulations were distinguished by using the modified dissolution apparatus and compared with those determined using the USP apparatuses Ⅱ and Ⅳ, and the dissolution capacities of the formulations were discriminated at different sampling time-points. The results of human bioequivalence (BE) studies in the fed state were consistent with in vitro evaluations that the maximum concentrations (C_max,in vivo) of both F1 and F2 fell below the acceptable range (80.00%). A level A IVIVC between the absorption fraction in vivo and dissolution in vitro, and a level C correlation between C_max,in vivo and C_{max,in vitro}, were established to guide the optimization of the tablet formulation containing MMF.

Original and generic preservation solutions in organ transplantation. A new paradigm?

Solid organ transplantation is a very complex process, in which the storage of the graft in a preservation solution is mandatory in order to extend ischemic times and contain further damage. The condition in which the organ is transplanted is critical for the outcome of the organ recipient. The recent emergence of generic versions of organ preservation solutions (solutions with the same composition and under the same legislation as the original versions, but with different brands) compelled us to study whether the standards are maintained when comparing the original and its generic counterpart. Along these lines, we discuss and comment on some aspects concerning this issue of general interest in the organ transplantation field.